1. Field of the Invention
This invention relates to surgical fasteners, and more particularly to two part bioabsorbable fasteners comprising a fastener member and retainer piece.
2. Background of Related Art
Surgical fasteners, or staples, are commonly used in surgical procedures to allow a surgeon to fasten body tissue quickly without the need for time-consuming suturing. Such surgical fasteners may be applied by surgical staplers singly, in succession, or a number may be applied simultaneously.
Some types of surgical fasteners are two-part devices. That is, they are composed of a fastener, or staple, portion, which is generally a pronged U-shaped member, and a retainer portion, which has apertures into which the prongs are engaged and held. Such fasteners, once engaged, are not separable. Therefore, once inserted into body tissue they cannot be easily removed. For this reason, two part fasteners are made of bioabsorbable material, such as glycolide, lactide, or copolymers of glycolide and lactide.
One such fastener is disclosed in U.S. Pat. No. 4,060,089 to Noiles. A fastener strip with multiple barbed prongs is disclosed, along with a retainer strip with a plurality of longitudinally spaced openings for receiving the prongs.
U.S. Pat. No. 4,402,445 to Green discloses a two pronged fastener with a retainer piece.
U.S. Pat. No. 4,506,670 to Crossley discloses a two part surgical fastener wherein the retainer piece is held to a supporting member by a lug with a frangible member. The prongs of the fastener, upon entering the aperture of the retainer, breaks the frangible member and pushes out the lug, thereby releasing the retainer piece from the supporting member.
U.S. Pat. No. 4,513,746 to Aranyi et al. discloses a two piece fastener. The fastener portion has two prongs with outer channels. The retainer piece has extensions with apertures for receiving the prongs of the fastener, and longitudinally extending expansion slots.
U.S. Pat. No. 4,805,617 to Bedi et al. discloses a surgical fastener system comprising parallel rows of staples and receivers with the receivers connected to adjacent receivers by a plurality of linkages.
U.S. Pat. No. 4,667,674 to Korthoff et al. discloses a surgical fastener having an extended base to reduce hemostasis.
U.S. Pat. No. 4,610,250 to Green discloses a two part surgical fastener. The fastener member has four prongs which mate with four openings in the retainer member. The two inner prongs are bent toward each other by camming surfaces in the corresponding openings in the retainer.
U.S. Pat. No. 4,932,960 to Green et al. discloses a two part surgical fastener in which the retainer member is provided with slot means to facilitate introduction of fastener prongs.
The following U.S. Design patents also illustrate fasteners: U.S. Pat. No. Des. 280,931; U.S. Pat. No. Des. 286,441; U.S. Pat. No. Des. 286,180; U.S. Pat. No. Des. 286,442 and U.S. Pat. No. Des. 280,932.
In designing and fabricating absorbable surgical fasteners and retainers, there are two competing considerations which must be addressed: first, the fastener/retainer combination must have sufficient mass to achieve effective hemostasis when applied to tissue and second, the fastener/retainer must not be so large as to remain in the body, i.e., fail to absorb, within a prescribed period of time.
Thus, for example, U.S. Pat. No. 4,534,352 to Korthoff discloses a surgical fastener member with an increased surface area to volume ratio to achieve faster resorption. Korthoff '352 teaches that this increased ratio does not sacrifice tensile strength retention during the period of time necessary for fastened tissue to heal and provides sufficient mass to penetrate tissue without buckling.